Field of the Invention
The present disclosure is directed to a slack adjuster which automatically adjusts the slack in the brake rigging of a railway vehicle, and further, to a slack adjuster including a secondary interior sealing arrangement to prevent fluid, such as water, and contaminants from entering into and accumulating in the critical operating area of the slack adjuster which could interfere with the operation of the slack adjuster.
Description of Related Art
Slack adjuster assemblies have been employed in brake riggings to compensate for slack caused by wear induced in the brake pads, wheels, and other components in brake rigging during repeated braking applications. By controlling this slack, the brake piston travel is automatically maintained at the correct length to ensure maximum efficiency in the brake system. The slack adjuster is also used to automatically adjust the slack in the brake rigging for various other reasons. One reason is to maintain the brake cylinder piston rod travel distance within a prescribed limit, which is of particular importance in present day higher speed operations. In addition, today's trains have a greater number of cars due to better locomotive equipment. For these reasons, it is important that the piston rod travel of the brake cylinder be maintained at a relatively close tolerance in order to properly balance the fluid pressure, usually air, in the fluid cylinder with that in the reservoir. Another important reason is that the slack adjusters will provide a substantially more uniform braking force to be applied to each set of wheels on each car making up a train.
One example of a slack adjuster that is used in a wide variety of railway applications is a double-acting compression-type slack adjuster, which is described in U.S. Pat. No. 4,662,485 and incorporated herein by reference. This slack adjuster assembly includes an elongated hollow housing member restrained against rotation and pivotally connectable at a first end thereof to a brake rigging. An elongated rod member, which is restrained against rotation and pivotally connectable at a first end thereof to the brake rigging, is provided within this housing and has at least a threaded portion adjacent a second end thereof. The threaded portion of the rod member extends into and is reciprocally movable within the housing through a second end of the housing. A positioning means, such as a cone lock nut located within a cone nut housing portion, movable between respective first abutting engagement, disengagement, and second abutting engagement positions, is threadably engaged with the threaded portion of the rod member intermediate said ends thereof. The cone lock nut rotates about the threaded portion of the rod member when in the disengaged position thereby changing the length of the slack adjuster assembly by changing the relative longitudinal position between the housing and the rod member. A pair of opposite facing abutment surfaces positioned within a portion of the housing and a pair of opposed abutting surfaces carried by the cone lock nut for engaging respective adjacent surfaces to resist rotation of the cone lock nut about the rod member when the cone lock nut is in one of the respective abutting engagement positions thereby retarding the change in relative longitudinal position between the housing and the rod member are provided. A first urging means is positioned between the cone lock nut and an abutment surface carried by the rod member for urging the cone lock nut into the disengaged position. A second urging means is positioned between the first end of the housing and the cone lock nut for overcoming a force applied by the first urging means and for urging the cone lock nut into the first abutting relationship position. An overtravel control means located within an overtravel control housing is positioned to reciprocally move in a longitudinal direction adjacent the first end of the housing and is engageable with the second urging means for reducing the force applied by the second urging means to less than the force applied by the first urging means, thereby allowing the cone lock nut to move to the disengaged position. An overtravel control actuating means is positioned to engage the overtravel control means for actuating the overtravel control means in response to the travel distance of a brake cylinder piston connected to the brake rigging.
Other examples of slack adjusters include the Universal Model 2300-DJ, owned by the assignee of the present application, Ellcon National Model D-2000, and New York Air Brake Model KDR-482-E.
During use of the brake rigging the slack adjuster is exposed to various environmental conditions, including conditions where the slack adjuster is exposed to large amounts of fluid, such as water. This water and other contaminants from the environment can accumulate and become trapped within the critical operating area and near critical components of the slack adjuster, which can compromise the functioning of the slack adjuster. The exposure to water can be problematic especially when the outdoor temperature reaches the freezing point and water located on or within the critical operating components freeze up. In one example, such as in the Universal Model 2300-DJ, the critical operating area includes the cone nut, bearing race assembly, and the conical spring, all of which operate together to allow the slack adjuster to adjust the brake rigging of the railcars as needed. It can be appreciated that different slack adjuster designs may include additional and/or other components within the critical operating area.
Some slack adjuster designs include a wiper seal located within the overtravel control housing with the intended purpose of preventing all water from entering into the slack adjuster. However, when a slack adjuster is exposed to large amounts of water, this wiper seal can fail to block all of the water from entering into the critical operating area of the slack adjuster. Thus, in these instances, water and contaminates may enter into the critical operating area and deleteriously effect the components located therein, resulting in faulty operation of the slack adjuster. Accordingly, there is a need in the art to secure and seal the critical operating area to maintain optimal operation of the critical operating components of the slack adjuster by preventing accumulation of water and contaminants near the critical areas of the slack adjuster. The system for preventing this accumulation of water and protecting the critical operating area from contaminants must be adaptable to all slack adjusters and orientations of installation, such that the slack adjuster can be used in a wide array of environmental conditions.